Flask



FIG. 1 shows a perspective view thereof;

FIG. 2 shows a front view thereof;

FIG. 3 shows a side view thereof;

FIG. 4 shows a top view thereof; and,

FIG. 5 shows a bottom view of the present invention.

The broken line showing in FIGS. 1-4 is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a flask, as shown and described. 